铁在菜豆体内再转移效果的研究

用水培方法研究了遮光和铵态氮、硝态氮处理对菜豆铁再转移能力的影响.结果表明,遮光有利于铁从缺铁植物的其他部位向植物的新叶转移;NH_4^+-N 供应可改善菜豆新叶的铁营养状况;NO_2^--N 供应则增加根部铁的累积,影响铁向地上部分转移.

Synthesis,characterization and catalytic reactivity of pentacoordinate iron dicarbonyl as a model of the [Fe]-hydrogenase active site

Two mono iron complexes Fe（CO）2PR3（NN） （R = Cy （3）, Ph （4）, NN = o-phenylenediamine dianion ligand, N2H2Ph2-） derived from the ligand substitution of Fe（CO）3hPR3 by the NN ligand were isolated and structurally characterized by single crystal X-ray diffraction. They have a similar first coordination sphere and oxidation state of the iron center as the [Fe]-hydrogenase active site, and can be a model of it IR demonstrated that the effect of the NN ligand on the coordinated CO stretch- ing frequencies was due to its excellent electron donating ability. The reversible protonation/deprotonation of the NN ligand was identified by infrared spectroscopy and density functional theory computation. The NN ligand is an effective proton acceptor as the internal base of the cysteine thiolate ligand in [Fe]-hydrogenase. The electrochemical properties of complexes 3, 4 were investigated by cyclic voltammograms. Complex 3 catalyzed the transfer hydrogenation of benzoquinone to hydroquinone effectively under mild conditions.

Localized Corrosion and Phase Transformation of Simulated Archaeological Iron

The corrosion behaviors of simulated archaeological iron in solution （0.06 mol·L^-1 NaCl＋0.03 mol·L^-1 Na2SO4＋0.01 mol·L^-1 NaHCO3） simulating soil water composition was investigated by potentialdynamic polarization, constant potential polarization, and simulated occluded cell （O.C.） galvanostatic tests. X-ray diffraction （XRD）, energy dispersive spectrometry （EDS）, and scanning electron microscope （SEM） were used to study the corrosion morphology and the evolution of corrosion product. The objective was to discover the transformation process of archaeological iron, and determine the distribution of chlorinated corrosion products. The results showed that the presence of crevice, cavities, and channels facilitates the localized corrosion under rusts; the autocatalytic effect increases the concentration of Fe^2＋, Cl^-, and SO4^2- , and promotes local acidification within the crevices and cavities. Meanwhile, the phase transformation of corrosion products is concluded to proceed by means of two ways. One is that the ferrous ions are transformed into different kinds of FeOOH via the intermediate Fe（Ⅱ）-Fe（Ⅲ） hydroxyl-salt （i.e. Green Rusts）; the other is that the Fe^2＋ ions are transformed into FeCl2, FeCl3, and orange powders akaganeite at the crevices and cavities.

Effects of temperature change on elastic behavior of steel beams with semi-rigid connections

Based on the nonlinear displacement-strain relationship,the virtual work principle method was used to establish the nonlinear equilibrium equations of steel beams with semi-rigid connections under vertical uniform loads and temperature change.Considering the non-uniform temperature distribution across the thickness of beams,the formulas for stresses and vertical displacements were presented.On the basis of a flowchart for analysis of the numerical example,the effect of temperature change on the elastic behavior of steel beams was investigated.It is found that the maximal stress is mainly influenced by axial temperature change,and the maximal vertical displacement is principally affected by temperature gradients.And the effect of temperature gradients on the maximal vertical displacement decreases with the increase of rotational stiffness of joints.Both the maximal stress and vertical displacement decrease with the increase of rotational stiffness of joints.It can be concluded that the effects of temperature changes and rotational stiffness of joints on the elastic behavior of steel beams are significant.However,the influence of rotational stiffness becomes smaller when the rotational stiffness is larger.

Construction management through bot: Taiwan high speed rall case

One of the key elements in real estate management is streamlining the construction process. Thus, the facilities can be built on a faster, cheaper, and higher quality base. Consequently, it will enhance the owner’s competitiveness. Due to the high cost and lengthy duration of mega-construction projects in recent years, Build-Operate-Transfer (BOT) contracts are getting popular in delivering constructed projects in the public sector. With BOT, the public owners are able to focus on the effectiveness of fair resource allocation as well as bring the efficiency of private enterprise into governmental operations. This paper uses Taiwan High Speed Rail project to exemplify the BOT method in executing the constructed projects in the chain of real estate management processes. The paper explains the reasons for building HSR and adopting BOT approach. The detail of the HSR project and the feasibility analysis of the project will be presented in this paper. The feasibility analysis comprises the comparisons of different transportation means, the financial analysis, and other benefits from HSR. Finally, conclusions will be drawn.

Super-exchange and Exchange-Enhanced Reactivity in Fe_(4)S_(4)-Mediated Activation of SAM by Radical SAM Enzymes

[4Fe-4S]-dependent radical S-adenosylmethionine(SAM)proteins are a superfamily of oxidoreductases that can catalyze a series of challenging transformations using the common 5-d Ado radical intermediate.Although the structures and functions of radical SAM enzymes have been extensively studied,the electronic state-dependent reactions of the[4Fe-4S]clusters in these enzymes are still elusive.Herein we performed QM/MM calculations to elucidate the electronic state-dependent reactivity of the[4Fe-4S]cluster in pyruvate-formate lyase activating enzyme.Our calculations show that the electronic statedependent SAM activation by the[4Fe-4S]clusters in radical SAM enzyme is determined by both the super-exchange and exchange-enhanced reactivities.The super-exchange coupling in the[4Fe-4S]cluster favors the antiferromagnetic coupling between two neighbouring pairs,which results in theα-electron rather than theβ-electron donation from the[4Fe-4S]^(1+)cluster toward the SAM activation.Meanwhile,in the most favorable electronic state for the reductive cleavage of S-C5′,Fe4 would donate itsα-electron to gain the maximum exchange interactions in the Fe4-block.Such super-exchange and exchange-enhanced reactivity could be the general principles for reactivities of[4Fe-4S]cluster in RS enzymes.

Iron porphyrin with appended guanidyl group for significantly improved electrocatalytic carbon dioxide reduction activity and selectivity in aqueous solutions

Iron porphyrins have high activity and selectivity for electrocatalytic CO_(2)reduction reaction(CO_(2)RR)in nonaqueous solutions,but they usually display poor or moderate selectivity for CO_(2)RR in aqueous solutions because of the competitive hydrogen evolution reaction.Using water as the electrocatalytic reaction solvent is more favored because not only it is cheap,green and abundant but also it can sufficiently provide protons required for CO_(2)RR.Therefore,developing Fe porphyrins as electrocatalysts for efficient and selective CO_(2)RR in aqueous solutions is of both fundamental and practical significance.Herein,we report the design and synthesis of Fe porphyrin 1 with an appended guanidyl group and its electrocatalytic features for CO_(2)RR in both nonaqueous and aqueous solutions.In acetonitrile,Fe porphyrin 1 and its guanidyl-free analogue,tetrakis(3,4,5-trimethoxyphenyl)porphyrin 2,are both efficient for electrocatalytic CO_(2)-to-CO conversion,but the turnover frequency with 1(3.9´10^(5)s^(-1))is one order of magnitude larger than that with 2(1.7´10^(4)s^(-1)),showing the critical role of the appended guanidyl group in improving electrocatalytic CO_(2)RR activity.More importantly,in 0.1 mol L^(-1)KHCO_(3)aqueous solutions,1 showed very high selectivity for electrocatalytic CO_(2)-to-CO conversion with a Faradaic efficiency of 96%,while 2 displayed a Faradaic efficiency of 65%for the CO_(2)-to-CO conversion.This work is of significance to show the effect of appended guanidyl group on improving both activity and selectivity of Fe porphyrins for CO_(2)RR electrocatalysis.

Molecular-based conducting magnet

Molecular-based conducting magnet or magnetic conductor, is an overlap of organic conductor and molecular magnet. Due to the existence of ferromagnetism, antiferromagnetism and quantum magnetism in insulated charge-transfer salt, it becomes a common sense that magnetism is not good for conductivity. After the discovery of first molecular-based metallic ferromagnet, molecular-based conducting magnet with n-unit from organic conductor and magnetism from coordination counterion became a hot area. The metallic ferromagnet, semiconductor room-temperature ferrimagnet, metallic weak ferromagnet and supercon- ducting antiferromagnet have been discovered. The new molecular-based conducting magnet with higher conductivity and higher magnetic ordering temperature is expected.

Comparative transcriptomic insights into the mechanisms of electron transfer in Geobacter co-cultures with activated carbon and magnetite

Both activated carbon and magnetite have been reported to promote the syntrophic growth of Geobacter metallireducens and Geobacter sulfurreducens co-cultures, the first model to show direct interspecies electron transfer (DIET); however, differential transcriptomics of the promotion on co-cultures with these two conductive materials are unknown. Here, the comparative transcriptomic analysis of G. metallireducens and G. sulfurreducens co-cultures with granular activated carbon (GAC) and magnetite was reported. More than 2.6-fold reduced transcript abundances were determined for the uptake hydrogenase genes of G. sulfurreducens as well as other hydrogenases in those co-cultures to which conductive materials had been added. This is consistent with electron transfer in G. metallireducens-G. sulfurreducens co-cultures as evinced by direct interspecies electron transfer (DIET). Transcript abundance for the structural component of electrically conductive pili (e-pili), PilA, was 2.2-fold higher in G. metallireducens, and, in contrast, was 14.9-fold lower in G. sulfurreducens in co-cultures with GAC than in Geobacters co-cultures without GAC. However, it was 9.3-fold higher in G. sulfurreducens in co-cultures with magnetite than in Geobacters co-cultures. Mutation results showed that GAC can be substituted for the e-pili of both strains but magnetite can only compensate for that of G. sulfurreducens, indicating that the e-pili is a more important electron acceptor for the electron donor strain of G. metallireducens than for G. sulfurreducens. Transcript abundance for G. metallireducens c-type cytochrome gene GMET_RS14535, a homologue to c-type cytochrome gene omcE of G. sulfurreducens was 9.8-fold lower in co-cultures with GAC addition, while that for OmcS of G. sulfurreducens was 25.1-fold higher in co-cultures with magnetite, than in that without magnetite. Gene deletion studies showed that neither GAC nor magnetite can completely substitute the cytochrome (OmcE homologous) of G. metallireducens but compensate for the cytochrome (OmcS) of G. sulfurreducens. Moreover, some genes associated with central metabolism were up-regulated in the presence of both GAC and magnetite; however, tricarboxylic acid cycle gene transcripts in G. sulfurreducens were not highly-expressed in each of these amended co-cultures, suggesting that there was considerable redundancy in the pathways utilised by G. sulfurreducens for electron transfer to reduce fumarate with the amendment of GAC or magnetite. These results support the DIET model of G. metallireducens and G. sulfurreducens and suggest that e-pili and cytochromes of the electron donor strain are more important than that of the electron acceptor strain, indicating that comparative transcriptomics may be a promising route by which to reveal different responses of electron donor and acceptor during DIET in co-cultures.